The qualitative or quantitative determination of analytes in test samples continues to be important in the diagnoses of physiological and non-physiological conditions. The analysis of a test sample mixed with reagents results in a detectable signal which can be evaluated with the aid of instrumentation.
Methods and devices have been provided which give determinations of a variety of analytes in a test sample. Such devices generally involve an inlet port, at least one chamber, at least one capillary, a vent, and at least one reagent providing for a detectable signal. Additionally, several chambers, capillaries and reagents can be provided in a single device permitting complex determinations.
U.S. Pat. No. 4,756,884 to Biotrack, Inc. teaches a capillary flow device which detects antigns in blood samples. Reagents are supplied in the track which can affect blood clotting or antibodies which can cause changes in the flow of sample in the track pathway. U.S. Pat. No. 5,135,719 to Biotrack teaches a blood separation device which separates plasma from red blood cells by use of a filter. Capillary action drives the separation procedure.
Typically, such devices have vents on one of the surfaces of the device. The vent is required to allow air to be displaced as liquid fills the track. The vents on the surfaces are troublesome since they generally have to be added by a separate process step. Vent holes are also problem some in that an air bubble is typically trapped at the site of the vent hole. If the device is jostled, the bubble may move into the track and interfere with assay mechanics or detection. In addition, if the vent is large and the device is angled, liquid may leak out. These issues impart extra design constraints or manufacturing control to insure proper sizing and positioning of the vent hole. Moreover, where a long residence time in a particular chamber is needed in a multistep reaction, the vents may be closed and opened accordingly to control fluid flow.
U.S. Pat. 4,952,516 to Pall Corporation, teaches a self-venting diagnostic test device which includes a porous absorbent which draws liquid through a microporous medium. A liquophobic material vents gases while preventing liquid from passing through the gas vent.
These references fail to teach self-venting capillary diagnostic devices which can vent along the length of a track.